The Volumes of Gas Particles Are Assumed to Be Zero

#31 All gas particles are tiny. The volumes of gas particles are assumed to be zero. All gas behaviors behave identically. randomly moving and colliding not attracting or repelling each other Therefore, the identities of the gas particles are not relevant with regards to volume, pressure, and temperature, and moles (only grams)

Dalton’s law summarizes this observation.

Ptotal = P1 + P2 + P3 + …

The total pressure equals the sum of the partial pressures. The identity of the gas causing the partial pressure is not relevant See figure 13.7 at page 465

#32 Water always evaporates. Water vapor molecules will always join/mix with the gas being collected. Water vapor pressure must be subtracted from the total pressure to obtain the partial pressure of the desired gas. #33

determine the partial pressure of O2 given = 4.0 grams of O2 desired = partial pressure of O2 map -- steps grams  moles  partial pressure divide by PV = nRT molar mass nRT P = V

multiply by RT divide by V

4.0 g O2 1 mol 0.08206 Latm (65 + 273) K = 0.693407  0.69 atm (16.002) g 1 molK 5.0 L determine the partial pressure of He given = 4.0 grams of He desired = partial pressure of He map -- steps grams  moles  partial pressure divide by molar mass multiply by RT divide by V

4.0 g He 1 mol 0.08206 Latm (65 + 273) K = 5.547256  5.5 atm 4.00 g 1 molK 5.0 L use the partial pressures to determine the total pressure Ptotal = PO2 + PHe

0.69 + 5.5 6.19  6.2 #34 determine the total volume of gas in the mixture given = 3.0 mol of N2 given = 2.0 mol of O2 given = 1.0 mol of CO2 given = 10.0 atm (total pressure) desired = total volume

PV = nRT

nRT V = P

(3.0 + 2.0 + 1.0) mol 0.08206 Latm (25 + 273) K 10.0 = 14.672328  15 L 1 molK atm

use the total volume to determine the partial pressure of N2 (convert to torr)

PV = nRT

nRT P = V multiply by 760.0

3.0 mol 0.08206 Latm (25 + 273) K 760.0 torr = 3716.98976  3700 torr N2 1 molK 15 L 1 atm

use the total volume to determine the partial pressure of O2 (convert to torr)

nRT P = V

760.0 2.0 mol 0.08206 Latm (25 + 273) K torr = 2477.993173  2500 torr O2 15 1 molK 1 atm L

use the total volume to determine the partial pressure of CO2 (convert to torr)

nRT P = V

1.0 mol 0.08206 Latm (25 + 273) K 760.0 torr = 1238.996587  1200 torr CO2 1 molK 15 L 1 atm #35

Determine the partial pressure of O2 given temperature = 27° C (not used in Dalton’s Law) given total pressure = 772 torr given vapor pressure of water = 26.7 torr desired = partial pressure of O2

Ptotal = PO2 + Pwater

Ptotal - Pwater = PO2

772 - 26.7 = PO2

77 2 - 26 .7 74 .3 5  74 5 745 torr #36

Determine the partial pressure of O2 given total pressure = 755 mm Hg given vapor pressure of water = 23 mmHg desired = partial pressure of O2

Ptotal = PO2 + Pwater

Ptotal - Pwater = PO2

755 - 23 = PO2

755 - 23 732 732 mm Hg

use the partial pressure of O2 to determine the moles of O2 determined pressure = 732 mm Hg (convert to atm) given volume = 500.- mL (convert to L) given temperature = 24° C (convert to K) desired = moles of O2

PV = nRT

n PV = RT

500.- 1 molK 732 mm Hg 1.000 atm 1 L mL 1000 0.08206 Latm 760 mm Hg (24 + 273) K mL

-2 = 0.01975966  0.0198 mol O2 = 1.98 x 10 mol O2 #1 1. intramolecular forces between polar molecules with dipole moments 2. dipole-dipole attraction is stronger if the atom with the relatively low electronegativity is covalently bonded to a more highly electronegative atom 3. dipole-dipole attraction is stronger if the atoms causing the dipole moments are small 4. dipole-dipole attraction is absent if the dipole moments are cancelled out

#2 1. dipole-dipole interactions are stronger if the distance between polar molecules are smaller 2. they are short range forces

#3 1. dipole-dipole interactions between molecules containing hydrogen atoms bonded to a more highly electronegative atom

#4 1. hydrogen bonding is the intramolecular force found in water

2. dipole-dipole attraction is the intramolecular force found in H2S, H2Se, H2Te 3. hydrogen bonding is the strongest form of dipole-dipole attraction, so... 4. therefore, water has the highest boiling point

#5 1. dipole-dipole interactions only occur over short ranges 2. gas particles are far apart 3. dipole-dipole attraction becomes unimportant when particle are far apart

#6 1. noble gas atoms have electrons 2. electrons are constantly moving randomly 3. sometimes, a temporary-non-uniform distribution of electrons take place 4. one side of the atom has more electrons than the other 5. one side of the atom becomes instantly and temporarily slightly negative and the other side becomes instantly and temporarily slightly positive 6. an instantaneous dipole is formed 7. the instantaneous dipole causes London dispersion forces to be present 8. if the atoms are slowed down sufficiently 9. the London dispersion forces will cause the noble gas atoms to attract one another and liquefy and solidify

#7 a. London dispersion force b. London dispersion force c. dipole-dipole attraction/interaction/force (and London dispersion force) d. hydrogen bonding (and London dispersion force) #8 1. larger noble gas atoms have more electrons 2. atoms with more electrons have greater temporary-non-uniform distribution of electrons 3. greater temporary-non-uniform distribution of electrons causes stronger instantaneous dipoles 4. stronger instantaneous dipoles causes stronger London dispersion forces 5. stronger London dispersion forces require more energy in order for boiling to take place

6. therefore, larger noble gases have relatively higher boiling points than smaller noble gases

#9 1. some of the ethanol molecules are occupying the empty space found between the water molecules (weak answer) OR!!!!!! 1. the hydrogen bonding and dipole-dipole attractions between water and ethanol molecules are stronger than those between just water molecules or between just ethanol molecules 2. therefore, a water molecule will be closer to an ethanol molecule than water and other water molecules and ethanol and other ethanol molecules 3. therefore, a mixture of water and ethanol occupy less space